Moment arms depend on the angles between the articulating bones, as discussed in Chapter 5. Consult Spoor et al. (1990) and Spoor and van Leeuwen (1992) for more detailed depiction of moment arms as a function of the flexion angle of the knee and the ankle.

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.